Did you know that almost all modern cars have one or more O2 sensors, regardless of the make or model? Many drivers are not aware of this, as this is a reliable component that doesn’t require much attention. However, this is a sensor that can cause all sorts of driveability issues and affect overall engine performance when faulty. In this article, we will learn what the O2 sensor does and how to tell if you have a bad one.  

What is an O2 sensor?

Despite the differences in engine types and configuration, all cars have the O2 sensor on the exhaust side of the engine. As the exhaust gases out the engine and pass by it, this sensor measures the proportion of oxygen inside them. The ECU uses this data for adjusting the air-fuel mixture and other running parameters to achieve better efficiency. To ensure their cars will meet strict emission standards, most manufacturers install two separate O2 sensors. The upstream sensor is between the cylinder head and the catalytic converter, and it analyzes raw exhaust fumes. The other one, which we call a downstream sensor, is just behind the catalytic converter. The data from this sensor helps the ECU when determining if the exhaust system is in good condition.  

How to tell if the O2 sensor is bad?

Because of its simple design and absence of moving parts, O2 sensors are reliable and can last quite long. However, things like unfavorable driving conditions or engine running issues can lead to formation of deposits on the sensor. As a result, it will give inaccurate reading and cause various running issues. Other possible issues include various electrical things, ranging from damaged wiring to corroded or loose connectors. Depending on whether the faulty sensor is upstream or downstream, this can cause either running issues or poor fuel economy. In any case, a corresponding error code stored inside the DTC memory will help narrow down the problem.  

Is it hard to replace the O2 sensor?

Replacing the O2 sensor is not too complex, as it only involves undoing several bolts or unscrewing the sensor itself. However, deciding on which sensor needs replacement may be tricky. This is especially true on V-shaped engines, as these have two banks with separate sets of O2 sensors for each one. In addition, the access to the sensor itself is very limited and may require some special tools and sockets. During the replacement process, you also need to to disconnect the wire plug and spray some penetrating oil onto sensor threads. In the end, add some anti-seize to the threads when installing a new sensor and tighten it to specified torque.

How important is this service?

As we have explained in this article, checking and replacing the O2 sensor is a job that requires a methodical and organized approach. If you don’t have the right tools or don’t feel up to the job, consider hiring a professional. At FixMyCar, we have certified and seasoned technicians that can come to your home and solve all O2 sensor related problems. This will ensure that all important components are checked and your car is ready to hit the road. O2 sensors can significantly improve your fuel mileage and hence can save you fuel costs in the long run.